Boring bit



March 19, 1-929;

c. o. SAN DBERG BoRIN BIVT Filed March 17, 1926 Even/02"."

' 'CFIRL OSKRRSENDBERG Patented Mar. 19, 1929. p

Tar? orF es.

' cam. osKAR sannnnne. or ocansno, swnnniv. 1

Bonnie BIT.

Application filed'March 17'; 1926, Serial No. 95,17S,-a11d in Sweden February 11, 1925.

The present invention relates to a boring bit which is intended to replace the usual socalled spoon-bit or duck-nose bit, and simultaneously to render the bit suitable for use also for other materials than wood. The

usual spoon-bit is provided with a flute semi-circle, into the back edge at the end of the bit. It is thus this semi-circular portion which is put against the wood when the bit is 20 used. It is a generally experienced fact, however, that a spoon-bit of this old type does not remain in the center against which the bit was placed, but the bit will move around such center with the result that one is never sure to get the hole drilled at the exact desired point. Such spoon-bits will also as a rule splinter the wood on the back of the piece when the bit cuts through the same.

The purpose of the present invention is to produce a bit which is not encumbered with the disadvantages above mentioned, and by means of which it will be easy to drill a hole at the exact desired point and which will also produce smooth and clean holes without splintering or splitting the wood on the upper side or the lower. For this purpose the bit is broadly characterized by the fact that the edges of the flute-shaped cavity, which are parallel over part of their length, towards the end of the bit run out into a sharp point located on the axis of the bit, and are all the way out to said point in or approximately in one and the samefplane through the axis of the drill.

An embodiment of a bit according to the invention is illustrated in the accompanying drawing. Fig. 1 shows an elevation of the bit viewed towards the cavity. Fig. 2 is a cross section on the line IIII in Fig. 1, and Fig. 3 is an elevation at right angles to that shown in Fig. 1.

As will be evident from the drawing, the shape of the present bit corresponds to the shape of an ordinary spoon-bit in so far as it has a cutting edge 1 which is parallel to the axis of the bit at least in respect of part of its site said cutting edge 1 is the so-called back edge 2 of the bit which is also parallel to the axis of the bit at least in respect of part of its length, and between the cutting edgeand the back edge is the flute-shaped cavity 3.

The cutting edge 1 is at a greater radial dis- .1 and the back edge 2 is substantially cylindrical.

According to the invention the end of the bit is tapered substantially conically to a sharp point 5 located on the axis of the bit, in which point the cutting edge 1 as well as the back edge 2' and the outer surface 4 of le gth; Approximately diametrically OPPOJ.

the bit and the surface of the cavity 3 meet.

as shown in Figs. 1 and 3. Owing to this con-- ically pointed shape the bit will always remain in the center in which it was put, and the bit will give clean and smooth holes and will not splinter or split the wood either on the upper side of the same where the bit penetrates into the wood, or on the lower side of the piece when the bit cuts through the wood. It has also been found that with the present bit it is possible to bore holes more rapidly than with ordinary spoon-bits.

The upper end of the bit may be given aconcal or other suitale shape for enabling the bit to be mounted in a brace or boring machine, or the bit may be provided with a handle in which manner the bit becomes a very practical hand tool which may find a many-sided use in different trades, such as by carpenters,

electricians, machinists, harness-makers, upholsterers, farmers, or in the homes.

I claim i 1. A boring bit having a flute shaped cavity, the front. edge of said cavity constituting a cutting edge and being at a greater radial distance from the axis ofthe bit than the back edge, said edges converging in apoint in the axis of the bit.

2. A boring bit. having a flute-shaped cavi.- ty, the edges of said cavity being located substantially opposite each other relatively to the axis of the bit and being directed towards the same side, one of said edges forming the cutting edge of the bit and the other forming the back edge of the bit, said cutting edge being at. a greater radial distance from the axis of the bit than the back edge, said edgesbeing parallel over a portion of their 4. A boring bit having a flute shaped cavilength and running out towards the end of ty, the front edge of said cavity constituting the bitinto a sharp point located on the axis a cutting edge and being at a greater radial of the bit, said edges being all the Way out to distance from the axis of the bit than the 5 said point substantially ina plane through back edge and also being located slightly in 15 the axis of the bit. front of the diametrical plane through said 3. A boring bit as claimed in claim 2, in back edge, said edges converging in a point which the cutting edge is located slightly in in the axis of the bit. front of the diametral plane through the back 10 edge. 7 CARL OSKAR SANDBERG. 

